Osmia lignaria (Blue Orchard Bee)
Osmia cornifrons (Hornface Bee)
Osmia cornifrons was introduced to the U.S. from Japan in 1977; O. lignaria is native to the U.S. Osmia bees are excellent pollinators of early blooming plants such as Brassicaceae and fruit trees. They are used in up to 200 cages annually at NCRPIS.
They are a solitary bee species (individual female bees perform all the work required to maintain their own nesting cells) that work from 50 to 90 F (10 to 32 C) during the months of April through June. These bees are non-aggressive. Rearing is established for this bee; they are low cost and require little care.
In nature, Osmia bees rear their young in bamboo or reeds but this bee readily accepts artificial nests. At NCRPIS, Osmia are provided waxed paper straws (7.25 mm diameter and 152.4 mm long); the females use mud to create barriers between the up to eight cells formed in each straw. Straws are inserted into cardboard tubes to protect the developing larvae from parasitization. These straws are placed inside domiciles constructed from PVC pipe for protection from the elements.
Two different sizes of PVC domiciles are used at NCRPIS; small domiciles are used inside of field cages and large domiciles are used to obtain an annual increase of bees. Small domiciles are constructed from 5.1 cm diameter PVC pipe. The front of the domicile is cut at a 45 degree angle to protect the straws from rain; an end cap at the opposite end retains the straws within the pipe. Large domiciles are constructed from 7.6 cm diameter PVC pipe. The front of the large domicile is also angled; in addition a piece of mesh screen covers the opening to prevent injury to the straws by birds and other predators. Both sizes of domiciles are fitted with two eye-bolts on the top of the pipe; eye-bolts are used to secure the domiciles in place in cages or increase areas. The domicile is suspended from a piece of rebar by sliding the eye-bolts onto the short section of the rod. The rod is inserted in the southwest corner of the cage with the domicile entrance pointed to the south-southeast. Large domiciles are simply suspended from tree branches with twine run through the eye-bolts; domicile openings are directed toward the south-southeast.
One peculiarity of Osmia, is that once these bees have emerged from a domicile in a particular location, if the domicile opening is repositioned even a slight distance, the bees will abort use of the domicile and will die soon after. These bees cannot be confined to their domiciles without causing death either. Because of this habit of the Osmia, if movement of domiciles is required prior to the end of pollination (e.g. for pesticide application to caged plants), the old domicile must be retired from use and a new Osmia domicile or a different bee must be introduced to the treated cage.
The ca 7000 Osmia bees used at the NCRPIS annually are obtained through two methods. 1500 to 2500 bees are purchased from U. S. suppliers located in Utah. In addition, ca 6000 bees are obtained from the nest cells produced in the field cages as well as outlying increase sites.
Osmia domiciles are removed from the field in early July, once temperatures are too warm for bees to continue working. Domiciles must be handled gently to prevent dislodging developing larvae from pollen balls within the nest cells. The domiciles are placed in a rearing room maintained at ca 80 F (26.5 C) and 50 % RH until November. In mid-November the straws are removed from the domiciles and examined for completed cells. Groups of straws containing 100 bee pupae are wrapped in 2-ply tissues and then placed into large garbage bags with water-dampened sponges (two sponges per bag). The garbage bags of sorted straws are stored at 40 F (4 C) for the winter. In March, the straws are removed from winter storage and placed in PVC domiciles in preparation for the coming field season. Small domiciles receive 3 filled straws (ca 24 bee pupae) in a bundle of 16 total cardboard tubes. Large domiciles receive 5 filled straws (ca 40 bee pupae) in a bundle of 23 cardboard tubes. Domiciles are maintained at 40 F (4 C) until use. Domiciles are moved from cold storage to cages immediately as the first bees will emerge from domiciles within 24 hours after they are brought to warm temperatures.